Electrostatic generator



June 14, 1966 E. GARTNER 3,256,450

ELECTROSTATIC GENERATOR Filed July 18, 196:

United States Patent 3,256,450 ELECTROSTATIC GENERATOR Elie Gartner,Grenoble, Isere, France, assignor to Centre National de la RechercheScientilique, Paris, France, an agency of the French Government FiledJuly 18, 1963, Ser. No. 296,058 Claims priority, application France,July 25, 1962, 905,000, Patent 1,340,215 Claims. (Cl. 310-6) Thisinvention relates to generating apparatus and more particularly to anapparatus for stabilizing the operation of an electrostatic generator.

As is well known, in certain types of electrostatic generators there isprovided a pair of spaced-apart energizing means, customarily in theform of pulleys, which are interconnected by an endless belt or othersuitable conveyor. Upon the rotation of the pulleys, charges appearthereon under the action of the friction between the pulleys and thebelt. Each pulley is provided with an ionizing member in spacedrelationship with the belt. The charged pulleys serve as inductors toenergize the ionizing members such that the members charge the beltthrough influence. The charge received by the belt from one of theionizing members is conveyed to the other member, which functions as theoutput terminal of the generator.

The polarity of the charges on the energizing pulleys, and hence thepolarity of the generator, is determined by various parameters andparticularly by the characteristics of the contacting sufaces of thepulleys and the belt. However, even in cases in which information isavailable as to particular electrical properties of the materials usedfor the contacting surfaces, difliculties have been encountered in theprovision of an electrostatic generator having an output ofpredetermined polarity. These difficulties arise primarily because ofchanges in the frictional effects between the pulleys and the belt whichresult from the adsorption of ambient gases or vapors.

For certain types of materials, particularly in cases in which thematerials used for the pulleys are of different electrical conductivity,the polarity at the output of the generator may be accuratelyestablished. As an illustration, for a belt of a material such asnatural rubber, for example, if one of the pulleys is of an electricallyconductive material and the other is of substantially nonconductivematerial, the charges on the conductive pulley are of positive polarity,as is the generator output, while the non-conductive pulley is chargednegatively.

In many self-energizing generators of the type employed heretofore, thecharges one the pulleys exhibited a tendency to build up and werelimited only by the dielectric rigidity of the ambient gas inside whichthe generator operated. The buildup of charges on the pulleys produced afluctuation in the potential difference between each pulley and itscorresponding ionizing member. As a result, with a generator load ofsubstantially constant impedance, the current intensity and voltageapplied to the load exhibited similar fluctuations, and the operation ofthe generator was highly unstable.

One general object of this invention is to provide a new. and improvedgenerator of the electrostatic type.

More specifically, it is an object of this invention to provide aself-energizing electrostatic generator having a stabilized output ofpredetermined polarity.

Another object of this invention is to provide an electrostaticgenerator which is economical to manufacture and thoroughly reliable inoperation.

In one preferred embodiment of the invention, auxiliary ionizing meansis operatively associated with at least one of the pulleys or otherenergizing means of the generator. This ionizing means serves to limitthe charge carried by the associated pulley to substantially reducefluctuations in the current intensity and voltage at the Patented June14, 1966 ice generator output. In certain particularly goodarrangements, the auxiliary ionizing means is interposed between anelectrically conductive pulley adjacent the output ionizing member andan oppositely charged portion of the endless belt.

In some advantages embodiments, the generator also is provided withadditional auxiliary ionizing means which is effective to limit thecharge on the pulley adjacent the input ionizing member. The arrangementis such that a substantially constant potential appears at the generatoroutput.

The present invention, as well as further objects and advantagesthereof, will be understood more clearly and fully from the followingdescription of one illustrative embodiment, when read with reference tothe accompanying drawing, in which the single figure is a schematicrepresentation of a self-energizing electrostatic generator inaccordance with the invention.

Referring to the drawing, there is shown an endless belt 1 which isfabricated from natural rubber or other suitable non-conductivematerial. The belt 1 is trained around two pulleys 2 and 4 which arepositioned one above the other in spaced-apart relationship and serve asthe energizing means for the generator. The pulley 2 is substantiallynon-conductive and illustratively is fabricated from polyethylene, vinylchloride or other insulating material. The pulley 4, on the other hand,is formed of metal and is highly conductive.

Positioned in spaced juxtaposition with the insulating pulley 2 is aninput ionizing member 3. The ionizing member 3 is maintained in astationary position with respect to the pulley 2 and is at groundpotential. The member 3 is arranged in close proximity with the outersurface of the portion of the belt 1 in contact with the pulley 2.

In a similar manner, an output ionizing member 5 is disposed in closeproximity with the outer surface of the belt portion in contact with theconductive pulley 4. The member 5 is arranged in spaced relationshipwith the pulley 4 and is suitably insulated with respect to ground. Aswill be understood, the member 5 serves as the output terminal of thegenerator and is arranged for connection to the desired load (notshown).

In operation, the non-conductive pulley 2 is continuously rotated in aclockwise direction, as viewed in the drawing, to similarly rotate thebelt 1 and the metal pulley 4. As the pulleys rotate, the pulley 2 ischarged with a negative potential while the pulley 4 is chargedpositively. The charged pulleys serve as inductors and respectivelyenergize the ionizing members 3 and 5. The input ionizing member 3cooperates with the belt 1 to load the belt with positive charges,through influence, and the upwardly directed reach of the belt conveysthese charges to the output ionizing member 5. The ionizing member 5collects the poistive charges and also produces negative charges, againthrough influence, on the downwardly directed belt reach moving awayfrom the member 5 toward the member 3. The positive charges on themember 5 establish the positive output potential of the generator.

In the use of the various components described thus far, the positivepotential on the metal pulley 4 exhibits a tendency to build up more orless continuously until the dielectric rigidity of the air or other gassurrounding the generator breaks down. Thus, the difference in potential between the pulley 4 and the output ionizer 5 tends to increaseuntil a momentary arc appears therebetween. As a result, the voltagebetween the pulley and the output ionizer fluctuates to produce unstableoscillations in the output voltage of the generator.

The instability of the generator output is augmented by somewhat similarfluctuations in the potential difference between the negatively chargedpulley 2 and the input ionizer 3. Because the ionizer 3 is at groundpotential, the adverse effect of the build-up of charges on the pulley 2is not as substantial as that resulting from the charges building up onthe pulley 4. 'For many types of electrostatic generators, however, thecharge build-up on the pulley 2 has a substantial efiect on thegenerators instability.

In order to limit the positive charges carried by the metal pulley 4,there is provided an auxiliary ionizing member 6 in the form of aconductor. One end of the member 6 is electrically connected to thepulley 4, while the other end is maintained in spaced relationship witha portion of the apparatus having a substantially lower potential. Thus,in the illustrated embodiment, the free end of the member 6 is in spacedjuxtaposition with the downwardly directed reach of the belt 1. Asindicated heretofore, this reach carries negative charges from thepulley 4 to the pulley 2. The potential difference between the pulley 4and the downwardly directed belt reach is substantially greater thanthat between the pulley and the output ionizer 5.

Upon the build-up of positive charges on the pulley 4, current flowsthrough the auxiliary ionizing member 6 and is carried by an efiluviaacross the spark gap between the free end of the member 6 and thenegatively charged reach of the belt 1. This current is eflective tolimit the potential of the pulley 4, and hence the potential at theoutput ionizer 5, such that the fluctuations in the current intensityand output voltage of the generator are sub stantially reduced.

In cases in which it is advantageous to also limit the potential of theinsulating pulley 2, there is provided a second auxiliary ionizingmember 7 which likewise is in the form of a conductor. One end of theionizing memher 7 is in spaced but close proximity with the negativelycharged pulley 2 to define a spark gap therebetween. The member 7includes an ionizing portion 8 at its opposite end which is arranged inspaced juxtaposition with a portion of the apparatus having a potentialsubstantially different from that of the pulley 2. As an illustration,in the illustrated embodiment the ionizing portion 8 is spaced from theupwardly directed positive reach of the belt 1, although in other goodarrangements the portion 8 is connected directly to ground.

As the negative potential on the pulley 2 tends to increase, arcingoccurs across the gap between the pulley and the adjacent end of theionizing member 7 and also across the gap between the ionizing portion 8of the member 7 and the negative reach of the belt 1. A current path isthereby established between the pulley and the belt which serves tolimit the build-up of charges on the pulley. The arrangement is suchthat, for a generator load of constant impedance, the current intensityand voltage at the ionizer is substantially constant, and anyfluctuation in the generator output is eliminated.

Because of the non-conductive characteristics of the material for thepulley 2, coupled with the highly conductive characteristics of thematerial for the pulley 4, the output potential at the ionizing member 5is of positive polarity. In cases in which a negative generator outputis desired, the ionizing member 3 is suitably insulated from ground andserves as the output ionizer of the generator. The ionizing member 5, onthe other hand, is connected to ground and is eifective to transmitnegatively directed electrostatic charges to the belt 1. In this lattersituation, the auxiliary ionizers 6 and 7 again enable a substantialreduction in the fluctuations of the output voltage to provide stableoperation.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention, in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimed is:

1. In an electrostatic generator, in combination, first and secondenergizing means in spaced-apart relationship with each other, aconveyor movable along a predetermined path between said energizingmeans for establishing a positive charge on said first energizing meansand a negative charge on said second energizing means, a pair ofionizing means disposed along said path respectively adjacent said firstand second energizing means, one of said ionizing means cooperating withsaid conveyor for applying electrostatic charges thereto and the otherof said ionizing means cooperating with said conveyor for receiving saidelectrostatic charges, and auxiliary ionizing means operativelyassociated with at least one of said energizing means for limiting thecharge established thereon, said auxiliary ionizing means beingpositioned along said path subsequent to the ionizing means adjacentsaid at least one energizing means in the direction of movement of saidconveyor.

2. In an electrostatic generator, in combination, means including afirst energizing member of electrically conductive material and a secondenergizing member of substantially non-conductive material inspaced-apart relationship with each other, a conveyor extending betweensaid first and second members, a pair of ionizing means respectivelyadjacent said members, one of said ionizing means cooperating with saidconveyor for applying electrostatic charges of one polarity thereto andthe other of said ionizing means cooperating with said conveyor forreceiving said charges and for applying electrostatic charges of theopposite polarity thereto, whereby one of said members is charged with apotential different from that of the other member, and auxiliaryionizing means operatively associated with at least one of the chargedenergizing members and including a point electrode cooperating with anoppositely charged portion of said conveyor for limiting the potentialof said at least one member.

3. In an electrostatic generator, in combination, energizing meansincluding a first pulley of electrically conductive material and asecond pulley of substantially nonconductive material in spaced-apartrelationship with each other, an endless belt movable along apredetermined path between said pulleys for conveying electrostaticcharges therebetween, a pair of ionizing means disposed along said pathrespectively adjacent said first and second pulleys, one of saidionizing means cooperating with said belt for applying electrostaticcharges thereto and the other of said ionizing means cooperating withsaid belt for receiving said charges, said other energizing meansforming an output terminal for said generator, whereby said first pulleyis charged with a potential of positive polarity and said second pulleyis charged with a potential of negative polarity, and auxiliary ionizingmeans separate from said output terminal and interposed between saidfirst pulley and said belt for limiting the positive potential of saidfirst pulley, said auxiliary ionizing means including a point electrodepositioned along said path subsequent to the ionizing means adjacentsaid first pulley in the direction of movement of said belt.

4. In an electrostatic self-energizing generator, in combination,energizing means including a metal pulley and a pulley of insulatingmaterial in spaced relationship with each other, a non-conductiveendless belt operatively in- .ter-connecting said pulleys for conveyingelectrostatic charges therebetween, first ionizing means injuxtaposition with the portion of said belt adjacent said insulatingpulley for applying positive charges to said belt, second ionizing meansin juxtaposition with the portion of said belt adjacent said metalpulley for receiving said positive charges from said belt and forapplying negative charges thereto, said metal pulley being charged witha positive potential and said insulating pulley being charged with anegative potential, and auxiliary ionizing means connected to said metalpulley and in spaced proximity with the negatively charged portion ofsaid belt for limiting the positive potential of said metal pulley.

5. An electrostatic self-energizing generator of the character set forthn claim 4, in which said auxiliary ionizing means and said negativelycharged portion of said belt define a spark gap therebetween to providea current path between said metal pulley and said belt.

6. In an electrostatic self-energizing generator, in combination, firstand second energizing means in spaced relationship with each other, aconveyor interconnecting said energizing means for conveyingelectrostatic charges therebetween, first ionizing means injuxtaposition with the portion of said conveyor adjacent said firstenergizing means for applying positive charges to said conveyor, secondionizing means in juxtaposition with the portion of said conveyoradjacent said second energizing means for receiving said positivecharges and for applying negative charges to said conveyor, said firstenergizing means being charged with a negative potential and said secondenergizing means being charged with a positive potential, firstauxiliary ionizing means operatively associated with said firstenergizing means and defining a first spark gap with the positivelycharged portion of-said conveyor for enabling current flow between thenegative first energizing means and said positively charged portion, tothereby limit the negative potential of said first energizing means, andsecond auxiliary ionizing means operatively associated with said secondenergizing means and defining a second spark gap with the negativelycharged portion of said conveyor for enabling current flow between thepositive second energizing means and said negatively charged portion, tothereby limit the positive potential of said second energizing means.

7. In an electrostatic self-energizing generator, in combination,energizing means including an electrically conductive pulley and apulley of insulating material in spaced relationship with each other, anendless belt operatively interconnecting said pulleys for conveyingelectrostatic charges therebetween, first ionizing means injuxtaposition with the portion of said belt adjacent said insulatingpulley for applying positive charges to said belt, second ionizing meansin juxtaposition with the portion of said belt adjacent said conductivepulley for receiving said positive charges and for applying negativecharges to said belt, said conductive pulley being charged with apositive potential and said insulating pulley being charged with anegative potential, first auxiliary ionizing means interposed betweensaid conductive pulley and the negatively charged portion of said beltfor limiting the positive potential of said conductive pulley, andsecond auxiliary ionizing means interposed between said insulatingpulley and the positively charged portion of said belt for limiting thenegative potential of said insulating pulley.

8. 'In an electrostatic self-energizing generator, in combination,energizing means including a metal pulley and a pulley of insulatingmaterial in spaced relationship with each other, a non-conductive beltmovable along a predetermined path between said pulleys for conveyingelectrostatic charges therebetween, first ionizing means disposed alongsaid path in juxtaposition with the portion of said belt adjacent saidinsulating pulley for applying positive charges to one of the reaches ofsaid belt, second ionizing means disposed along said path injuxtaposition with the portion of said belt adjacent said metal pulleyfor receiving said positive charges from said one belt reach and forapplying negative charges to the other reach of said belt, said metalpulley being charged with a positive potential and said insulatingpulley being charged with a negative potential, first auxiliary ionizingmeans connected to said metal pulley and including a portion positionedalong said path subsequent to said second ionizing means in thedirection of movement of said belt and in spaced proximity with saidnegatively charged reach for limiting the positive potential of saidmetal pulley, and second auxiliary ionizing means for limiting thenegative potential of said insulating pulley, one portion of said secondauxiliary ionizing means being in spaced proximity with said insulatingpulley and another portion being positioned along said path subsequentto said first ionizing means in the direction of movement of said beltand in spaced proximity with said positively charged reach.

9. An electrostatic self-energizing generator of the character set forthin claim 8, in which the said portion of said first auxiliary ionizingmeans and the negatively charged reach of said belt define a spark gaptherebetween to provide a current path between said metal pulley andsaid negatively charged reach.

10. An electrostatic self-energizing generator of the character setforth in claim 9, in which said second auxiliary ionizing means enablesthe flow of current between said insulating pulley and the positivelycharged reach of said belt, to reduce the negative potential of saidinsulating pulley.

References Cited by the Examiner UNITED STATES PATENTS 2,836,785 5/ 1958Neubert 3106 3,056,052 9/ 1962 Hand 310-6 FOREIGN PATENTS 535,924 1/1957Canada. 587,731 11/1962 Canada. 808,355 7/ 1 Germany. 1,009,712 6/1957Germany. 1,081,557 3/ 1960 Germany.

773,031 6/ 1957 Great Britain.

MILTON O. HIRSHFIELD, Primary Examiner. I. W. GIBBS, Assistant Examiner.

1. IN AN ELECTROSTATIC GENERATOR, IN COMBINATION, FIRST AND SECONDENERGIZING MEANS IN SPACED-APART RELATIONSHIP WITH EACH OTHER, ACONVEYOR MOVABLE ALONG A PREDETERMINED PATH BETWEEN ENERGIZING MEANS FORESTABLISHING A POSITIVE CHARGE ON SAID FIRST ENERGIZING MEANS AND ANEGATIVE CHARGE ON SAID SECOND ENERGIZING MEANS, A PAIR OF IONIZINGMEANS DISPOSED ALONG SAID PATH RESPECTIVELY ADJACENT SAID FIRST ANDSECOND ENERGIZING MEANS, ONE OF SAID IONIZING MEANS COOPERATING WITHSAID CONVEYOR FOR APPLYING ELECTROSTATIC CHARGES THERETO AND THE OTHEROF SAID IONIZING MEANS COOPERATING WITH SAID CONVEYOR FOR RECEIVING SAIDELECTROSTATIC CHARGES, AND AUXILIARY IONIZING MEANS OPERATIVELYASSOCIATED WITH AT LEAST ONE OF SAID ENERGIZING MEANS FOR LIMITING THECHARGE ESTABLISHED THEREON, SAID AUXILIARY IONIZING MEANS BEINGPOSITIONED ALONG SAID PATH SUBSEQUENT TO THE IONIZING MEANS ADJACENTSAID AT LEAST ONE ENERGIZING MEANS IN THE DIRECTION OF MOVEMENT OF SAIDCONVEYOR.